Analysis of pulse-labeled fibrinogen in the transfected CHO cells. The cells were pulse-labeled for 1 hour with [³⁵S]-methionine and chased for the indicated periods with an excess of unlabeled methionine. The recombinant fibrinogen and/or 3 polypeptides of fibrinogen were then immunoprecipitated from the cell lysates or the conditioned media with a rabbit antihuman fibrinogen antibody and protein A-Sepharose. The immunoprecipitates were subjected to electrophoresis on 4% to 12% gradient SDS-PAGE under nonreducing conditions and autoradiography. Lane Inh in (A) included the addition of purified plasma fibrinogen to the reaction mixtures of the 6-hour chase experiment to demonstrate the antibody specificity. Lane PC in (B) was the conditioned medium at the 6-hour chase of γ153C as a positive control.